* Re: [PATCH] assorted delta code cleanup
2005-06-29 6:49 4% [PATCH] assorted delta code cleanup Nicolas Pitre
@ 2005-06-29 7:10 7% ` Matthias Urlichs
0 siblings, 0 replies; 2+ results
From: Matthias Urlichs @ 2005-06-29 7:10 UTC (permalink / raw)
To: git
Hi, Nicolas Pitre wrote:
> This is a wrap-up patch including all the cleanups I've done to the
> delta code and its usage.
FWIW, I think Linus said he'd prefer a do/while loop. In fact this old
code ...
> -static unsigned long parse_delta_size(unsigned char **p)
> -{
> - unsigned char c;
> - unsigned long size = 0;
> - unsigned shift = 0;
> - unsigned char *data = *p;
> -
> - do {
> - c = *data++;
> - size += (c & 0x7f) << shift;
> - shift += 7;
> - } while (c & 0x80);
> - *p = data;
> - return size;
> -}
> -
... is IMHO much more readable than this ...
> +static inline unsigned long get_delta_hdr_size(const unsigned char **datap)
> +{
> + const unsigned char *data = *datap;
> + unsigned char cmd = *data++;
> + unsigned long size = cmd & ~0x80;
> + int i = 7;
> + while (cmd & 0x80) {
> + cmd = *data++;
> + size |= (cmd & ~0x80) << i;
> + i += 7;
> + }
> + *datap = data;
> + return size;
> +}
> +
(except that the first += should be |= ).
Yeah, I know, it's nitpicking. Regard it as a testimony to the code's
quality that I didn't see worse. ;-)
NB, it might be a good idea to exit with an error if the shift exceeds 31.
--
Matthias Urlichs | {M:U} IT Design @ m-u-it.de | smurf@smurf.noris.de
Disclaimer: The quote was selected randomly. Really. | http://smurf.noris.de
- -
When it's fall in New York, the air smells as if someone's been frying
goats in it, and if you are keen to breathe the best plan is to open a
window and stick your head in a building.
-- The Hitch Hiker's Guide to the Galaxy
^ permalink raw reply [relevance 7%]
* [PATCH] assorted delta code cleanup
@ 2005-06-29 6:49 4% Nicolas Pitre
2005-06-29 7:10 7% ` Matthias Urlichs
0 siblings, 1 reply; 2+ results
From: Nicolas Pitre @ 2005-06-29 6:49 UTC (permalink / raw)
To: Linus Torvalds; +Cc: Junio C Hamano, git
This is a wrap-up patch including all the cleanups I've done to the
delta code and its usage. The most important change is the
factorization of the delta header handling code.
Signed-off-by: Nicolas Pitre <nico@cam.org>
diff --git a/count-delta.c b/count-delta.c
--- a/count-delta.c
+++ b/count-delta.c
@@ -6,23 +6,9 @@
#include <stdlib.h>
#include <string.h>
#include <limits.h>
+#include "delta.h"
#include "count-delta.h"
-static unsigned long get_hdr_size(const unsigned char **datap)
-{
- const unsigned char *data = *datap;
- unsigned char cmd = *data++;
- unsigned long size = cmd & ~0x80;
- int i = 7;
- while (cmd & 0x80) {
- cmd = *data++;
- size |= (cmd & ~0x80) << i;
- i += 7;
- }
- *datap = data;
- return size;
-}
-
/*
* NOTE. We do not _interpret_ delta fully. As an approximation, we
* just count the number of bytes that are copied from the source, and
@@ -44,15 +30,14 @@ int count_delta(void *delta_buf, unsigne
unsigned char cmd;
unsigned long src_size, dst_size, out;
- /* the smallest delta size possible is 4 bytes */
- if (delta_size < 4)
+ if (delta_size < DELTA_SIZE_MIN)
return -1;
data = delta_buf;
top = delta_buf + delta_size;
- src_size = get_hdr_size(&data);
- dst_size = get_hdr_size(&data);
+ src_size = get_delta_hdr_size(&data);
+ dst_size = get_delta_hdr_size(&data);
added_literal = copied_from_source = out = 0;
while (data < top) {
diff --git a/delta.h b/delta.h
--- a/delta.h
+++ b/delta.h
@@ -9,4 +9,26 @@ extern void *patch_delta(void *src_buf,
void *delta_buf, unsigned long delta_size,
unsigned long *dst_size);
+/* the smallest possible delta size is 4 bytes */
+#define DELTA_SIZE_MIN 4
+
+/*
+ * This must be called twice on the delta data buffer, first to get the
+ * expected reference buffer size, and again to get the result buffer size.
+ */
+static inline unsigned long get_delta_hdr_size(const unsigned char **datap)
+{
+ const unsigned char *data = *datap;
+ unsigned char cmd = *data++;
+ unsigned long size = cmd & ~0x80;
+ int i = 7;
+ while (cmd & 0x80) {
+ cmd = *data++;
+ size |= (cmd & ~0x80) << i;
+ i += 7;
+ }
+ *datap = data;
+ return size;
+}
+
#endif
diff --git a/diff-delta.c b/diff-delta.c
--- a/diff-delta.c
+++ b/diff-delta.c
@@ -306,12 +306,13 @@ void *diff_delta(void *from_buf, unsigne
*orig = i;
}
- /* next time around the largest possible output is 1 + 4 + 3 */
if (max_size && outpos > max_size) {
free(out);
delta_cleanup(&bdf);
return NULL;
}
+
+ /* next time around the largest possible output is 1 + 4 + 3 */
if (outpos > outsize - 8) {
void *tmp = out;
outsize = outsize * 3 / 2;
diff --git a/pack-objects.c b/pack-objects.c
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -34,7 +34,7 @@ static void *delta_against(void *buf, un
if (!otherbuf)
die("unable to read %s", sha1_to_hex(entry->delta->sha1));
delta_buf = diff_delta(otherbuf, othersize,
- buf, size, &delta_size, ~0UL);
+ buf, size, &delta_size, 0);
if (!delta_buf || delta_size != entry->delta_size)
die("delta size changed");
free(buf);
diff --git a/patch-delta.c b/patch-delta.c
--- a/patch-delta.c
+++ b/patch-delta.c
@@ -20,36 +20,20 @@ void *patch_delta(void *src_buf, unsigne
const unsigned char *data, *top;
unsigned char *dst_buf, *out, cmd;
unsigned long size;
- int i;
- /* the smallest delta size possible is 4 bytes */
- if (delta_size < 4)
+ if (delta_size < DELTA_SIZE_MIN)
return NULL;
data = delta_buf;
top = delta_buf + delta_size;
/* make sure the orig file size matches what we expect */
- cmd = *data++;
- size = cmd & ~0x80;
- i = 7;
- while (cmd & 0x80) {
- cmd = *data++;
- size |= (cmd & ~0x80) << i;
- i += 7;
- }
+ size = get_delta_hdr_size(&data);
if (size != src_size)
return NULL;
/* now the result size */
- cmd = *data++;
- size = cmd & ~0x80;
- i = 7;
- while (cmd & 0x80) {
- cmd = *data++;
- size |= (cmd & ~0x80) << i;
- i += 7;
- }
+ size = get_delta_hdr_size(&data);
dst_buf = malloc(size);
if (!dst_buf)
return NULL;
diff --git a/sha1_file.c b/sha1_file.c
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -592,22 +592,6 @@ void * unpack_sha1_file(void *map, unsig
return unpack_sha1_rest(&stream, hdr, *size);
}
-static unsigned long parse_delta_size(unsigned char **p)
-{
- unsigned char c;
- unsigned long size = 0;
- unsigned shift = 0;
- unsigned char *data = *p;
-
- do {
- c = *data++;
- size += (c & 0x7f) << shift;
- shift += 7;
- } while (c & 0x80);
- *p = data;
- return size;
-}
-
static int packed_delta_info(unsigned char *base_sha1,
unsigned long delta_size,
unsigned long left,
@@ -645,11 +629,12 @@ static int packed_delta_info(unsigned ch
* the result size. Verify the base size while we are at it.
*/
data = delta_head;
- verify_base_size = parse_delta_size(&data);
- result_size = parse_delta_size(&data);
+ verify_base_size = get_delta_hdr_size(&data);
if (verify_base_size != base_size)
die("delta base size mismatch");
+ /* Read the result size */
+ result_size = get_delta_hdr_size(&data);
*sizep = result_size;
return 0;
}
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2005-06-29 6:49 4% [PATCH] assorted delta code cleanup Nicolas Pitre
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